I have a 94 E320 58000 miles. The vehicle operates flawlessly. Smooth idle, 22 MPG fuel ecnomy, no problems in starting, engine temperature stays between 80 and 95. Everything works fine, except the Check Engine Light. I always get DTC 19 code a few days after resetting and along with it either 3 or 4.

Arther and Suginami are helping me. I have the following checks planned. Pin 8 and see why code 19 is coming up. I will also check the fuel pressure regulator and try to clean the EGR Tube and see what happens.

Enigne Gasket, Aux fans, EGR valve and wiring harness have been replaced. 60000 mile service has also been done, new spark plugs, air, fuel filter, transmission etc.

Mercedes Benz dealer diagnosed my problem as follows:
Function Test W/HHT/ HFM Codes 035 O2 Sensor
Stop/Mixture to lean, 051 Self Adapt too rich, Replace O2 sensor still at Rich stop, Replaced Mass Air still reads flat, Replace over voltage relay, reading still flat, Diag Faulty HFM Control Module $2200.

If anyone else has any idea's or similar past experiences, please let me know. Steve and Jim seem to be the experts on the Bosch Control Modules on this site. I did notice that the LH-SFI module had some software issues.




94 E420 Check Engine Light On

ATTN TECHS

<< Stop/Mixture to lean, 051 Self Adapt too rich>>

AllData -code 035 e320-124 chassis 104 eng HFM-SHI

O2 sensor system operating at rich limit, mix too lean

Remedy/Causes:

Intake air leak
Fuel injectors
Reg pressure diaphram

BC you also see an AIR code fault, I would look at the vac hose
that goes from the engine intake , front of engine [ white plastic hose under front engine cover ] to the AIR/EGR Switch over valves... on 104s , these dry out and break, causing an air intake leak [ causing the lean condition] and that will bring up the AIR and/or EGR codes along w/19 ..just a possible, but common 104 problem....
Post what you find at pin 8 on HFM-SFI module...that will help
I don't think HFM-SFI computer had the problem of the LH-SFI

I have purchased all the neccessary stuff from Radio Shack to make the LED/SE tool. I also bought the Sears Multimeter with the duty cycel. I was trying to see if the multimeter can be used for the engine codes, but after researching, have found that the LED/SW tool is the best method to get the Codes.

Will post the codes as soon as the Check Engine light comes on again. Has been off since I reset it a few days back. It still has code 19. I believe the Check Engien Light only turns on when DM gets a second code like 3,4 or 5.

__________________
Zafar
94 E320 58000 Miles

>

Don't have to wait for CE lamp indication to retrieve stored codes from other modules..
CE only comes up when faults effect emmissions paremeters..
So, go to both 8 and 14 and see what is in there..
Pin 1 is gnd [ neg], pin 16 is positive [ 12v] and the odd colored
wire goes to appropriate pin [in this case , both 8 and 14]

Arthur,

I got the following codes:

DM LED Code 1

PIN 8 Code 13 (O2 system at rich limit, mixture too lean, Intake air leak, fuel injectors, diaphram pressure regulator)

PIN 14 Code 5 (Stop lamp switch S9/1). The instrument panel light bulb warning had come on. I Replaced a brake light bulb a few days back. Maybe that's what this one is.

I opened the front engine cover and looks like all the vaccum lines are in good shape and connected.

I repeated the procedure a few times to make sure that no other codes were present, and the codes above kept on repeating. I did not clear the codes.

__________________
Zafar
94 E320 58000 Miles

Now clear all codes and see what comes back...

Looks like everything is pointing to a fuel pressure check.

What dissapoints me most is the level of expertise at Mercedes Benz dealerships. William Auto World in East Lansing, MI has recommended changing the ECM after getting Code 35 (Mixture lean) without check the Fuel Pressure!

Rock Hill Imports in Kingsport, TN just changed the Wiring Harness, and informed me Friday that they could not cover the wiring harness under the goodwill policy, after talking to the factory rep, due to the age of the car! Delarship in Atlanta has done this for hundreds of cars. I will have to talk to the factory rep myself. Wiring harness did not need to changed at that time, the ECM Code has not changed.

I gave Rock Hill Imports the print out from this FORUM on the LH ECM, mixture too rich, on the second visit for the same Check Engine Light problem, and the tech concluded that changing the module was the the correct diagnosis based on DM CODE 19, wihtout realizing that LH is different from HFM! and no other testing.

I requested them to change the Aspirator Motor for the climate control and they changed the Cabin Temp Sensor, I had to tell the service manager Grag Durham where the motor was and he agreed to refund the labor and parts for the sensor change. Aspirator was on the service requested form for the Tech!

I had requested Williams Auto World East Lansing, MI to change the ACC cabin filters and they informed me that my car had did not have any!! They did not know that the filters are located below the windshield wipers.

Both the dealers above handle both Mercedes and BMW. Hard to believe!! They should have checked the fuel pressure after getting the code from ECM. None of them did, $2200.00 (ECM Change) MI dealer, I declined, and $884 TN dealer (wiring harness) which they did, and it did not solve the problem. If I had know about the harness issue, I would have gone to the Atlanta dealer and got it replaced under the Goodwill policy, but at that time, I was not aware of the this FORUM.

I would like to thank everyone on this FORUM again for the help and the information data base that has been created.

__________________
Zafar
94 E320 58000 Miles

Arthur,

I cleared all the codes and got Code 1 from, both Pin 8 and 14. I started the car, turned it off and checked again. Code 1 again from both Pin 8 and 14.

__________________
Zafar
94 E320 58000 Miles

Code 1 is No Codes stored [ simply meaning you have successfully cleared the faults from the memory of each module]

Now drive the car and go back in a couple of days ..

Don't wait for CE lamp, as that only comes on after other module
detected faults talk to DM and DM decides if that fault will effect emmissions..if it does not , CE won't come on even if other mods have stored codes..[that is why we go to other mods when you get ignition/fuel related probs that finally get to CE/emmissions paremeters]

Unfortunately, this means of diagnosis really is limiting. The info that is necessary is the adaptation numbers and you must have a scanner for that.

The code 19 problem happens in any system. It means you have reached the limit of electronic adaptation. The LH problem arose over LH systems in hot humid climates that got richer with great regularity. At lower partial adapt numbers of about .85 the limit was reached.

OBDII cars have the same problems with lean running AMMs where they bump the limits at 1.32 or so. They trip P0170 and P0173 codes. But notice the numbers. The early cars only had 15% correction built into the software. The MB solution was new software encased in new hardware. As Jim and others have found, that software rides on a 36k chip that is easily readable and new ones programmed. Why MB makes everyone buy the hardware over is beyond me. Anumber of companies allowed updated software by just replacing the chips (BMW, Volvo and GM come to mind)

Part of the point is that with failures the system logically can't correct for ever. The new ones with 32% mixture correction on both sides of the original equation 1.000 are really amazing.

So when dealing with this issue the amount of correction is one consideration, but solving the deviation is another. If the mix has gone rich due to pressure changes then fixing that is the point.

If the thing runs "rich" at .85 and still has closed loop control then software can solve the problem. New software (MB list at over 1800 usually) will allow that .85 car to go to probably .68. The 119 LH cars that were fixed with software seemed to get long term correction at about .82 from what I have seen and heard. In these cases the software is a good solution.

I am pretty certain I have had code 19 on HFM cars that were at the .85 not .68 level.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

I didn't know that E320 engines developed the "dreaded" DTC19 problem.

Of course, I know that V8s from '92 to '95 develop this problem and recently, it happened to me. The fix was to change the eprom which was successful. Monitoring the SA after the replacement eprom show a continued 'downward' trend to 0.8319.

At that point, I replaced the O2 and MAF sensors. After a month plus, the SA when back to 0.8534 at the last measurement.

But replacing BOTH of those parts is not cheap! An added bonus, was the increase in gas milage to 16mpg on the last fillup. At CA prices, it may pay for the parts, soon!

__________________
Regards . . . . JimF
-------------------
'94 S500 Cpe

Visit my Mercedes Web Page

I believe that in my case it is border line. I reset the code in the ECM module, Code 035 W/HH and code 13 with impulse scanner(Mixture too lean, O2 at Rich stop limit), drove the car for 35 miles, checked the codes and got Code 1 (No system faults). Over a period of time, it probably goes a little above the 15% adaptation limit and then gives the code.

But, I agree with Steve, the proper fix is to correct the Air/Fuel supply issues.

My fuel economy is in the 20-24 MPG range. Does running lean have any adverse affects on the engine?

__________________
Zafar
94 E320 58000 Miles

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Interestingly enough, I have had 104 code 19s that were vac related [lean] and the fix on one was a intermittant /sticking open purge valve.. [ common part failure on these]. MOT on left fender well... feel for pulsations..archieves
This was finally found by plugging each vac system and driving the car for periods, waiting for a code.

The other was a sticking EGR valve .. this is also common on 104s and there is a TSB out on the part replacement..
Both of these vac leaks are a little tricky to find BC they are Internal leaks and intermittant..
The EGR was easier BC I also had EGR codes.. but the purge did not code out..
Granted , I did not have access to limit values at the time , but have not had a code 19 return on either since...[2 yrs]

Check Engine light came on, right after starting. Got the following codes:

DM Code 4 (Air Injection inoperative)
Code 19 (Fuel Injectors open/short or Emission system at adaptation limit)

Pin 8 Code 13 (O2 at rich limit, mixture too lean)
Pin 14 Code 1 (No faults)

WJM replaced the chip. I would like to replace the chip as well to increase the adaptation range, along with Air/Fuel supply investigation. Below is what WJM wrote about the LH chip mod:


"I have a copy of the Service Bulletin that I received from Steve some time ago. Post your fax # and I can send it to you.

As closure to this particular issue. It turns out the the difference between the computer Mercedes recommends upgrading to and the original is the software on the chip... and at that only 18 bytes of it.

I've run into a few additional people who have had this problem. We went ahead and simply replaced the chip with the newer version (got a copy from someone who had the new computer) and it has so far solved the issue and eliminated the check engine light #19 code.

Willy"

Willy, what is the procedure for upgrading the chip?

__________________
Zafar
94 E320 58000 Miles

Arthur's expertise for your car.

I can 'repair' this problem for V8s but do not have a chip for the 6's.

WJM (Willy) and a group of people, including myself, had problems with V8s. And I can supply a chip for any of these cars that fixes the problem. BUT NOT FOR 6s. Maybe WJM has this capability???

__________________
Regards . . . . JimF
-------------------
'94 S500 Cpe

Visit my Mercedes Web Page